"Error: Unable to retrieve stack list" when Clicking on Orchestration/Stacks in Horizon and heat CLI will fail with unauthorized error message

Issue

• When clicking "Orchestration/Stacks" or "Orchestration/Resource Types" in Horizon, the following errors are seen:

    Error: Unable to retrieve stack list
    Error: Unable to retrieve stack resource types

• All heat CLI commands will fail with an unauthorized error message

• In /var/log/horizon/horizon.log, the following errors are logged:

2015-09-01 06:23:17,061 12852 WARNING horizon.exceptions Recoverable error: ERROR: You are not authorized to complete this action.
2015-09-01 06:23:20,550 12851 WARNING horizon.exceptions Recoverable error: ERROR: You are not authorized to complete this action.
2015-09-01 06:26:50,736 12850 WARNING horizon.exceptions Recoverable error: ERROR: You are not authorized to complete this action.